1. Field of the Invention
The present invention relates to a method of and an apparatus for the measurement of gas properties which may be determined from a volume flow rate and/or a pressure difference such as the dynamic viscosity and the density of fuel gases using a device to control the flow of the gas so measured and at least one flow restrictor.
2. Description of Related Art
A method of and an apparatus for the flameless measurement and/or control of heat input into gas appliances of a similar nature are known from the European Patent Application No. 0 022 493. Said application reveals a method of and an apparatus for the measurement of the dynamic viscosity and the density of fuel gases and of other fuel gas properties such as the higher heating value, the lower heating value or the Wobbe index. According to the teachings of said application, at least part of the gas to be analyzed is passed through a laminar flow restrictor taking the form of a capillary tube for dynamic viscosity measurement and through a turbulent flow restrictor taking the form of an orifice plate for density measurement. Said application further proposes a series connection of said laminar flow restrictor and said turbulent flow restrictor for the purpose of measuring both dynamic viscosity and the density of a fuel gas for determining the higher or the lower heating value of said gas. To determine said dynamic viscosity and said density, it is necessary to obtain at least two measured values namely the pressure difference across the appropriate flow restrictor and the volume rate of flow expressed in terms of volume per time of the gas passing across said flow restrictor. The measurements proposed by said application are made continuously, as the gas to be measured continues to flow, determining the upstream and the downstream flow restrictor pressures, thence a total of five values having to be measured and to be combined for obtaining the dynamic viscosity and the density of the gas being measured. The gas so flowing continuously must for the purposes of the application of said method further be discharged into a main gas line or into a line taking said gas to a gas-fired appliance or gas-fired equipment. It is an object of the present invention to simplify the method of measurement and the measurement apparatus of the kind indicated above.